Electrically controlled phase shifters use varactor
diodes or nonlinear dielectrics.
The series portion is designed with two interdigital capacitors and two varactor
diodes [D.sub.S1] and [D.sub.S2] connected in parallel.
A 5-5.47 GHz LC-VCO using varactor
configuration in 0.18 um CMOS, in Proceedings of the 2nd International Conference on Signal Processing and Integrated Networks (SPIN 2015), 19-20 February 2015, Noida, India, 87-89.
The tunnel diodes used in our prototypes are various Germanium models ranging from General Electric 1N3713 to 1N3717  whereas the varactor
diodes are the low-capacitance and hi-Q type Silicon Abrupt Junction Tuning Diodes (SMV1405 series, Skyworks, Inc.).
By switching the varactor
diodes that load the dipoles of the FSS, the reflection coefficient is modulated.
To implement the high-speed mode using digital three- point modulation, a dual-varactor circuit technology was developed that, when in high-speed mode, increases the variation in the varactor
's capacitance at the VCO, which takes the high-frequency modulated signal as input.
- To implement the high-speed mode using digital three-point modulation, a dual-varactor circuit technology was developed that, when in high-speed mode, increases the variation in the varactor
's(3) capacitance at the VCO(4), which takes the high-frequency modulated signal as input.
This model is chosen because of the range of capacitance effect of the varactor
which is sufficient to tune the filter from 2 GHz to a desired minimum center frequency of 1 GHz (using (15), [C.sub.r] is approximately equal to 2 pF).
The probe fed microstrip antenna design consists of a ground plane, an air gap of 60 mils to accommodate the varactor
diodes, a single layer of Rogers RO 4232 substrate and the patch on top.
In [5-9], tunable one stop-band filters are proposed based on varactor
loaded split ring resonators, RFMEMS metamaterials and DGS respectively.
In addition, the varactor
contribution is represented by a bias-dependent capacitance [C.sub.ds].
Tuning LC parameters at a fixed frequency can be obtained by incorporating varactor
diodes  and/or tunable inductor chips  along the structure.